This invention relates to a pump dispenser of the type sometimes called a xe2x80x9ctrigger sprayerxe2x80x9d in which the piston reciprocates vertically and is provided with a downward tubular inlet stem connected to an opening in the piston head. Liquid passes through the tubular stem and opening into the cylinder chamber. More specifically, this invention relates to the structure of the piston and an inlet check valve insert installed on such a piston and adapted to close the opening.
The prior art, of course, is replete with varieties of manual pump dispensers adapted to pump liquid out a discharge orifice from a container on which the dispenser is mounted. One variety of such a dispenser is shown in the McKinney U.S. Pat. No. 4,161,288 in which the piston comprises a tubular inlet stem leading up to an opening in the piston head through which liquid passes into the pumping chamber. The piston seal is in the form of a plastic insert which seals the piston to the cylinder wall. The seal includes a central check plug aligned with the opening by webs integral with the piston seal and plug.
When the piston is raised by the trigger, the central plug seats on the opening blocking exit of the liquid back through the inlet. It raises on the downstroke to permit liquid to flow into the chamber.
Other check valves on the piston have included a steel ball operable in a special chamber and small enough to raise to permit passage of liquid on the downstroke, but dropping to close the tubular stem on the upstroke.
The invention is defined in the claim language. To be brief, the invention is a pump dispenser comprising a cylinder and piston assembly. The assembly is defined by a piston head and a tubular downward stem adapted to pass liquid up through an opening in the center of the piston head and into the cylinder chamber. A plastic check valve insert is installed in the upper side of the piston head. It comprises a one-piece molded wheel-like element including a securing rim fitting into an annular trough in the piston head, a central hub adapted to valve off the opening at the top of the tubular stem and a plurality of zig-zag spokes connecting the rim to the hub. These zig-zag spokes may each be in the form of arcuate portions concentric with the axis of the piston and inner and outer radial portions integral with the ends respectively of the arcuate portion.